It's oft said that "not more than a degree or 2 at most" ... bu, taken in context.
a) A $170 AIO will, at most have a degree or 2 difference between it and a $50 air cooler .... 98% of those will not cool better than that air cooler and 100% of the AIOs that get close to itr will be louder
b) Its also can be the difference between a $35 air cooler and a $90 air cooler.
As to the old MX-2 .... Has it been opened ? May be dried out or at least viscosity is thicker making spreading harder.
Benchmarkreviews did an outstanding 80 way TIM test, and also a "How to apply" article ... the finding showed that the best method depoended on the type of cooler being used. Coolers with the copper pipes that can be seen at the bottom benefitted from applications of lines at the edges of the pipes. Overall the pea size method was most universally beneficial (with exceptions) but only if the pea was 1/4 the size of a real pea. I miss referring to those articles as the site has poofed. As I'm sure some might be curious , at the time, the 80 way test had AS5 and Shin Etsu G751 at a tie for best thermal performance. AS5's took hits for its 200 hours of thermal cycling to cure and for it being capacitive.... small risk but always felt 0 is better than small. Thens Thermal Grizzly knocked those from the top spot,
If the tube of MX-2 was opened , then I'd toss ... if not, try it. If it's shot (too thick to spread) .... In recent years, Shin Etsu has gotten hard to find at the historic $3.95 price and Thermal Grizzly Kryonaut has come down to normal $8 -ish price levels .. so with everything around the same price these days, no reason not to get the top performer ... you can spring for the metal conductive types but the cost and risk turns many away.
